My 06 KA has developed the fault where the heater is constantly on hot (damn hot). I have replaced the heater control valve because had one of those stop working before and still no good. I connected the multimeter to the plug for the HCV and was not getting any reading (constant 0V).

This made me think is it the heater control panel that is faulty (not sending the signal to the HCV). By default no signal would keep the HCV open and hence constantly on hot. Or could it be a blown fuse for the control panel?

Does anyone have any ideas? What wires would I test on the control panel to see if a signal was being sent to the HCV if I got a new control panel? Anyone know what fuse the control panel works off? The handbook just lists about 21-22 fuses, I am sure there must be more then that for the car.

I was checking my KA the other day and noticed the coolant was down to the min mark, I had topped it up to the max mark a couple of weeks before.

The car is used every day (Mon - Fri) so if there was a problem I would expect to see the level go down quicker. I topped it up and run the engine and did not see any loss under the car and it seemed to stay at the max level.